Research: Structural alterations of the pulmonary arteries in primary pulmonary hypertension (PPH) are characterized by medial muscular thickening and complex vascular lesions known as plexiform lesions. Three-dimensional computerized reconstruction of plexiform lesions from PPH and secondary pulmonary hypertension (PH) patients using endothelial cell (EC) specific markers, shows that the pulmonary ECs of plexiform lesions are in different developmental stages and that their proliferation markedly impedes pulmonary blood flow. The overall goal of this proposal is to examine the effects of shear stress and angiogenic regulators on EC growth and function-as a means to understand the pathogenesis of PH associated with plexiform lesions. We hypothesize that shear stress causes increased VEGF and/or VEGF receptor expression, leading to endothelial cell dysfunction and proliferation. Since Angiopoietin (Ang)1, Ang2, and VEGF cause progressive maturation and organization of ECs lining blood vessel lumina, we also hypothesize that the angiogenic ligands (VEGF, Ang1, Ang2) interact with each other and their tyrosine kinase receptors to maintain an embryonic vasculogenic phenotypic growth. To study the mechanistic questions related to the role of ECs in the genesis of plexiform lesions in PPH, we will use a three-dimensional, microvascular EC culture system for systematic studies of angiogenesis in vitro. Preliminary work with the chronic flow system demonstrates a morphologic similarity between the shear-stressed, three-dimensional, in vitro ECs and shear stress conditions will be analyzed with the use of recombinant growth factors or inhibitors of the tyrosine kinase regulation, proliferation, and growth in non-PPG conditions, such as tumor angiogenesis, wound repair and healing , female reproduction, and diabetic retinopathy. Candidate and Environment: Formal mentorship in the lab of Dr. Rubin Tuder will continue throughout the time of this proposal. During this proposal period, I will acquire the independence in though and investigative methods required for the transitions to independent status as a funded researcher, with interest and expertise in the area of experimental pulmonary pathology. An Advisory Committee has been established to aid my academic career development.